Method of dyeing leather with azoic dyestuffs and products so produced



United States Patent 015cc 3,409,384 Patented Nov. 5, 1968 3,409,384 METHOD OF DYEING LEATHER WITH AZOIC DYESTUFFS AND PRODUCTS SO PRODUCED Clemens Streck, Loudonville, N.Y., assignor to GAF Corporation, a corporation of Delaware 5 No Drawing. Filed Apr. 22, 1965, Ser. No. 450,209

' 13 Claims. '(Cl. 8-13) ABSTRACT OF THE DISCLOSURE This invention relates to the dyeing of leather and relates more particularly to procedures for dyeing leather with azoic dyestuffs and to the products so-produced. As pointed out in U.S. Patent No. 2,913,301, it has long been the desire in the trade to be able to dye leather in such a manner that the color is fast to washing, crocking, and light. However, the conventional acid, direct, and basic colors generally are lacking in these necessary fastness properties and frequently have a tendency to bleed when treated in a soap liquor. Running of the colors with prior art dyeings obviously decreases the brightness of the dyestutf in addition to causing staining of nearby garments or other areas of the same garment. Attempts have been made to dye leather by the azoic method such as, for example, by application of a diazo component. However, due to the high alkalinity of the coupling component treating liquor, this material exhausted poorly, the conditions for eflicient coupling with the diazo component were improper, and the shades ob- -tained were dull, weak and of poor wash-, crock-, and

light-fastness. Further, the quality of the leather was detrimentally atfected, various desirable properties thereof being destroyed. t

In U.S. Patent 2,913,301 a method described which overcomes to a great extent the difiiculties of azoic dyeing of leather. However, this method depends for its workability on a careful adjustment of pH during the dyeing procedure. Such a degree of pH control is not always desirable or possible in a dye plant.

Thus, it is a primary object of this invention to provide a process for the azoic dyeing of leather free from the foregoing and other disadvantages.

Basically, it is an important objective of this invention to provide a process for the production of leather dyed with azoic colors having good wash-, crock-, drycleaning, and/or light-fastness properties.

A further object of this invention is the provision of a process for the azoic dyeing of leather which will produpe uniform, level shades and will not adversely affect desirable properties in the leather.

Still another object of this invention is to carry out azoic dyeing of leather with a minimum of pH control during the dyeing.

Other objects and advantages will in part be obvious and in part be pointed out as the description of the invention proceeds.

Consistent with the above objects, the instant inventive concept comprises, in an azoic dyeing method, the step of treating leather with an aqueous solution of an azoic coupling component, devoid of solubilizing groups, in the presence of an a-sulfo substituted long chain fatty acid.

It has been found that application of the coupling component in this manner enables the attainment of wash-, crock-, and/ or light-fast dyeings having good penetration and having no detrimental efiect on desirable properties in the leather. In contradistinction to the usual dyeing methods which emphasize surface imperfections in the leather, the instant process minimizes such imperfections whereby an upgrading effect is attained and the product is thereby particularly commercially desirable.

The leather to be treated in accordance herewith may be wet from a tanning treatment or it may be wet out in usual manner with water which may desirably contain a wetting agent. It the leather is highly acid, the addition of some sodium bicarbonate or other alkaline material to the wetting-out liquor is desirable to aid in neutralizing the acidity and preventing it from unduly affecting the pH of the coupling component treating liquor. Accordingly to this invention, this wet leather is then treated with an aqueous solution of a long chain m-sulfoalkylcarboxylic acid. Preferably, and in order to obtain the best results, this treatment of the leather is prior to treatment with the coupling component, although treatment with these materials may be simultaneous.

The aqueous solution containing the coupling component is prepared by dissolving the coupling component with sufiicient alkali, such as sodium or potassium hydroxide, to form the alkali metal salt of the coupling component plus a small excess to prevent too early hydrolysis, but insufficient excess to raise the pH of the solution to any significant extent.

During impregnation of the leather with this solution, it may be desirable to control the pH of the solution to a pH of about 7 or less. In most cases this is accomplished by gradual addition of an acid, such as acetic, hydrochloric or preferably formic acid, during and preferably towards the end of the impregnation treatment. In some cases, especially where the leather is sufliciently acid to start with, for example, as the result of a previous tanning or other treatment, the treatment with acid may be dispensed with.

The temperature oftreatment may vary from about room temperature to about F., with durations of about 15 minutes to 2 hours. Optimum conditions are dependent in any particular instance upon the nature of the leather and the treating agents employed, being readily determinable by a worker in the art.

With some coupling components, the addition of a small amount of a water soluble organic solvent such as ethyl alcohol, isopropyl alcohol, ethylene gycol and its monoethyl ether or the like may be desirable to facilitate solution thereof. Further, the addition of a wetting agent to the solution, or other similar additives, may be desirable in some instances.

The long chain a-sulfoalkylcarboxylic acids found particularly useful in the process of this invention are those which have from twelve to eighteen carbon atoms, such as a-sulfolauric acid, a-sulfopalmitic acid, and a-sulfostearic acid. The long chain a-sulfoalkylcarboxylic acid is dissolved in water of solution strength which may range from about a 10 percent solution to saturation and the already wet leather is impregnated with the solution in an amount ranging from about 0.2 percent to 5 per cent of the a-sulfoalkylcarboxylic acid based on the weight of the leather.

The coupling components operative in the instant invention are the usual ice color coupling components devoid of solubilizing groups such as sulfonic or carboxylic acid groups and well known in the art. In general, these coupling components may be characterized as compounds having an active methylene group, an enolizable keto group or an aromatic hydroxy group including coupling,

usually in orthoor para-position, preferably the former, to said hydroxy group. Such compounds are typified by the acylacetarylides, the pyrazolones, and aromatic hydroxy compounds capable of coupling.

As acylacetarylides there may be mentioned acetoacetic acid arylides, furoylacetic acid arylides, terephthaloyl-bisacetic acid arylides, and the like. It should be mentioned that when acylacetarylides are employed, formaldehyde, which is frequently used in the dyebath, should be excluded as it tends to react with this type of coupler.

As pyrazolones, there may be mentioned 1-phenyl-3- methyl-S-pyrazolone, 1- (p-tolyl -3-methyl-5-pyrazolone, 3-methyl-5-pyrazolone, S-pyrazolone, 1,3-dimethyl--pyrazolone, 'l-(p-chlorophenyl)-3-methyl-5-pyrazolone, 1- (p-nitrophenyl)-3-methyl-5-pyrazolone, 1 (o-anisyl) 3- methyl-S-pyrazolone, 1- (m-aminophenyl) -3-methyl-5-pyrazolone, l-methyl-S-pyrazolone, l-phenyl-S-pyrazolone, 1-phenyl-5-pyrazolone-3-carboxylic acid methyl and ethyl esters, and other pyrazolones unsubstituted or substituted in the 1- and/ or 3-positions by non-solubilizing radicals.

The aromatic carbocyclic or heterocyclic hydroxy compounds useful as coupling components herein generally include phenols, resorcinols, 1- and 2-naphthols, benzonaphthols, hydroxybenzofluorenones, 4-(5-chloro-2-hydroxyphenylazo) resorcinol, and its copper derivative, and the like, in addition to arylides of fi-hydroxyaromat-ic carboxylic acids. Illustratively, examples of arylides of B- hydroxyaromatic carboxylic acids which may be employed in the process of the instant invention are 3-hydroxy-2-naphthoic acid arylides, 3-hydroxy-2-anthroic acid arylides, 3-hydroxy-2-carbazole-carboxylic acid arylides, 3-hydroxy-2-furane-carboxylic acid arylides, 2-hyd roxy-llH-benzo [a] carbazole-3-carboxylic acid arylides, hydroxydibenzothiophenecarboxylic acid arylides and the like.

Many such coupling components operative herein are disclosed in Diserens, Chemical Technology of Dyeing and Printing, volume 1, pages 213 to 224 (Reinhold Publishing Corp., 1948); Lubs, Chemistry of Synethetic Dyes and Pigments, pages 182 thru 192 (Reinhold Publishing Corp., 1955); and Adams, Journal of the Societyof Dyers and Colourists, volume 67 (1951), be ginning at 223. 1

One of the coupling components set forth above must be reacted with a diazotized aromatic primary amine also devoid of solubilizing groups such as carboxylic or sulfonic acid groups in order to produce the azoic dyeing on the leather. As examples of such primary amine compounds useful in the instant invention, there may be mentioned aminoazotoluene, 4-chloro-2-nitroaniline, 5-chloro-o-toluidine, 4-nitro-o-toluidine, 2,5-dichloroaniline, 4- benzamido-2,S-diethoxyaniline, 4-nitro-m-anisidine, 4mitro-o-anisidine, 4-chloro-o-anisidine, l-aminonaphthalene, l-amino-anthraquinone, dianisidine, 5-chloro-4-nitro-oanisidine, aminobenzophenones, aminosulfones such as aminobenzosulfones and amino-diphenylsulfones, aminodiphenyl ethers, aminocarbazoles, and other similar cyclic compounds containing at least one diazotizable primary amine group. Such canbocyclic and heterocyclic azoic bases as the above and other operative in the process of this invention are well known in the art.

The diazotizable aromatic primary amine compound to be reacted with the coupling component may be applied subsequent to the application of the coupling component to the leather, or simultaneously therewith. In either case, the final azoic dyestuff is produced by treatment of the leather containing the coupling component and diazotizable amine with conventional diazotizing agents which take the form of sodium nitrite and an acid preferably formic acid, whereby diazotization of the amine and reaction of the resulting diazo compound with the coupling component takes places in situ on and/or in the leather.

Even better results are obtained by application of the aromatic amine in the form of its already diazotized compound, whereby a subsequent diazotization treatment with sodium nitrite and acid'is avoided. These diazo compounds may be employed as a solution freshly prepared from a diazotizable amine or as a solution of one of its stabilized salts, e.g., as a hydrochloride or sulfate of one of the relatively stable diazos, as a double salt employing such salts as zinc chloride, zinc sulfate, cadmium chloride, tin tetrachloride, fluoroborates and the like, or as a salt with an organic acid such as benzenedisulfonic acid, ,Et-naphthalenesulfonic acid, and naphthalenetrisulfonic acid.

In some instances wherein solubility may be insufiicient a dispersing agent may be added to improve dispersion and penetration. Further, the subsequent application of the amine may be in the form of its nitroso compound or as the stabilized diazo amino compound, e.g., the Levamines.

All of these forms of stabilized primary amino compounds or nitrosoamines are to be regarded as the equivalent of the freshly prepared diazotized primary amine compounds since they react as such with the coupling component.

Alternatively, but not as preferably, the aromatic primary amine compound can be applied to the leather in its diazotized form simultaneously with the coupling component in a known manner. Thus, the coupling component can be combined with a stabilized form of the diazotized primary amine compound, such stabilized compound being activated by dropping the pH to 7 or less, whereby the coupling reaction takes place in situ on and/or in the leather. Examples of known types of combinations of coupling components and stabilized diazotized primary amine compounds are the Rapidazols (mixtures of couplers and diazosulfonates), the Rapid Fast colors (mixtures of couplers and antidiazotates), and preferably, the Rapidogens (mixtures of couplers and diazo amino compounds).

As a further alternative, the leather may be sprayed on one side with an ice color coupling component such as described above and over sprayed with a diazotizable amine or diazotized amine,'with the color developed in the manners described above.

In general, the diazo component and the coupling component are employed in amounts sufficient to react in approximately equivalent proportions, although in some cases it may be desirable to use an excess of one. The reaction products thereof, i.e., the azo dyestulf itself, is provided in amounts ranging from about 0.1 to 10 percent, and preferably from about 0.1 to 5 percent based on the weight of the leather.

The following examples, wherein percents are by weight based on the weight of the leather unless otherwise indicated, are illustrative of the instant invention and are not to be regarded as limitative. These Examples disclose various embodiments and means for carrying out the basic process of the invention more fully described above.

Example 1 A 10 gram piece of chrome tanned calf leather in the blue was washed and the pH adjusted to about 6-7. To this bath which contained cc. of water was added 1 percent of wsulfostearic acid as a 15 percent by weight solution. After 20 minutes there was added 8 percent of formaldehyde and 3 percent of monoethanolamine. After 5 minutes there was added three percent of Naphthol AS-OL (3-hydroxy-2-naphth-o-anisidide), 5 percent of alcohol, and 3 percent of caustic soda (34 B.). After 20 minutes 1 /2 percent of formic acid was added. After 20 more minutes 2 percent of formic acid was added. After another 20 minutes and without dropping the Naphthol bath, 8 percent of Fast Orange Salt GGD (zinc chloride double salt of diazotized 3,5-hexafluoroxylidine) was added directly to the bath. Fifteen minutes later the leather was rinsed, treated with 2 percent soap Example 2 Example 1 was repeated with the exception that the u-sulfostearic acid was replaced by 1 percent of a-sulfopalmitic acid as a 25 percent by weight solution.

The dyeing was equally as uniform, bright and strong as in Example 1, in contrast to a non-uniform dull, weak dyeing obtained when carried out without the treatment with a-sulfopalmitic acid.

Example 3 Example 1 was repeated with the exception that the a-sulfostearic acid was replaced by 1 percent of a-sulfolauric acid as a 25 percent by weight solution.

The dyeing was equally as uniform, bright and strong as in Example 1, in contrast to a non-uniform dull,

weak dyeing obtained when carried out without the treatment with a-sul-fopalmitic acid.

Example 4 Chrome tanned calf leather was treated as in Example 1 with 1 percent of a-sulfostearic acid, 3 percent Naphthol AS-OL and for-mic acid. Then 8 percent of Fast Olive Salt B (zinc chloride double salt of diazotized 6-(2-chloro-4-nitro-phenylazo)-3,4-dimethoxyaniline) and 20 percent of urea was added to the bath. The dyeing was finished as in Example 1.

A uniform deep blackish olive was obtained, in contrast 6 A bloomy black was obtained. AATCC wash test No. 2 showed no staining on multifi-ber (6 fibers) material.

When sulfur colored bottom suede (a suede that has been previously colored with a sulfur brown or black) was colored in this same manner the shade was jetter.

Example 12 Sulfur brown bottom suede and sulfur black bottom suede were both wet back. To the baths were added 1 percent of m-sulfostearic acid. After 20 minutes 8 percent of formaldehyde and 3 percent of monoethanolamine were added. After 5 minutes 3 percent of Naphthol AS-BB dissolved with 5 percent alcohol and 2 percent caustic 34 B. was added. After about 20 minutes at 100 F. 1 /2 percent of formic acid was added, after about 20 minutes 2 percent of formic acid was added and the heat shut off. After another 20 minutes the pH was adjusted to 7-8 with sodium bicarbonate. Then 1 percent of Rosanthrene Base (0.1. 17780) and /2 percent of Fast Blue B Base Diazo were added. After 15 minutes sodium bicarbonate was added to a pH of 6.5-7.5. After 15 minutes it was rinsed and scoured.

A bluish brown was obtained on the sulfur black bottomed leather, and a jet brown on the sulfur brow bottomed leather.

Examples 13-l6 Sixteen samples of sulfur brown bottomed leather were treated as in Example 12 to the point of adding the diazo with the exception that the Naphthol AS-BB was replaced by 2 /2 percent of Naphthol AS-OL.

To these solutions were added the following:

Exam 1e to the non-unr-fonm, very weak, dull olive WhlCh was obp tained when the wsulfostearic acid was omitted. 13 14 5 16 Fast Orange Salt GGD, percent 1 2 l 3 Examnples gast lglavy 3l1ueB Salt RApercent 2 2 1 2 The following dyeings were made in the manner of U122, .33mi...1 322353211133: .1. 1; 1% 1i 1% 7 Example 1.

Example Coupling Component Fast Color Salt Shade 5 Naphthol AS-OL 8% Fast Navy Blue Salt RA Deep Navy.

- [4-(2,G-dichloro-l-mtro-phenylazo)-2,5dimethoxyaniline, diazotized and stabilized with zinc chloride]. 6 2% Naghthol AS-FGGR 5% Fast Red Salt PDC Bright Green. 1 (Pht alocyanine type cou- [(5-N-hutylsulfamyl)-o;an1srd ne,

pling component). diazotrzed and stabrhzed with zinc chloride]. 7-; 1% Resorcinol 8% Fast Red Salt PDC Yellowrsh-Qrange. 8 2% Naphthol AS-BB 5% Fast Garnet Salt GBO Deep Blackrsh [4-(5-chloro-2-methoxyphenyl- [4-(o-tolylazo-2-methylbenzene Brown.

az0)-6 or7-hydroxy-1- diazonmm sulfate]. naphthylamine]. 9 2% Naphthol AS-D 8% Fast Black Salt ANS.. Deep Black. [3-hydroxy-2-naphth-o- [a mixture of Fast Black Salt G toluidide]. and Fast Black Salt K]. 10 2% Naphthol AS-D 8% Fast Navy Blue Salt RA BllllSh Black.

Example 11 After 15 minutes, sodium bicarbonate was added to 2 Chrome tanned suede leather in the blue was rinsed as in Example 1 and the pH was adjusted to 6.5-7 with sodium bicarbonate. 1% of wsulfostearic acid was added to the bath. After 20 minutes 8% of formaldehyde and 3% of mono'et hanolarnine were added. After 5 minutes a solution of 2 percent of Naphthol AS-D, 5 percent of alcohol, and 2 percent of caustic 34 B. was added. After 20 minutes at aboulclOO-IIO" F. 1 /2 percent of formic acid was added, and after 20 more minutes the heat was shut off and 2 percent more of formic acid was added. After another .20 minutes 7 percent Fast Navy Blue Salt RA was added. Fifteen minutes later sodium bicarbonate was added to a pH of 6.5-7.5. After 15 more minutes the treated leather was rinsed, soaped and rinsed again and then given an acidified rinse.

pH of 6.5 to 7.5. After 15 minutes the pieces of leather were rinsed and finished.

The shades obtained varied from greenish black browns to deep jet browns with practically no staining of multifiber material on Wash Test No. 2.

Example 17 Two samples of chrome tanned sheep skin in the blue were washed. Both were treated in identical manner except that one solution was treated for 20 minutes with 1 /2 percent of a-sulfostearic acid and the other was not. This was followed by addition of 8 percent of monoethanolamine and 4 percent of formaldehyde. After 5 minutes /2 percent Naphthol AS-D dissolved with 3 percent of alcohol and 2 percent of caustic soda 34 B. was added. After 20 minutes at F. 1% percent of formic acid was added. After another 20 minutes 2 percent of formic acid was added and the heat turned off. After 20 minutes more 1% percent of Fast Olive Salt B and 5 percent of urea were added. After 20 additional minutes, the leather was rinsed and finished as usual.

The untreated sample was a weak, uneven gray whereas the treated sample was a strong, evenly dyed gray.

Example 18 Two samples of chrome tanned sheep skin in the blue were treated as in Example 17 with the exception that the Fast Olive Salt B was replaced by 8 percent of Fast Navy Blue Salt RA.

In the case of the untreated material, the dyeing was a weak unevenly dyed leather, and in the case of the treated sample the dyeing was a rich, strong, even, pleasing blue having excellent color value.

Example 19 A gram piece of crusted chrome tanned sheepskin was treated for 20 minutes at 100 F. in a bath which contained 100 cc. of water and 1 /2 percent of a-sulfostearic acid. 8 percent of formaldehyde and 4 percent of monoethanolamine were added. After 5 minutes there was added 2 percent of Naththol ASOL, 5 percent of alcohol, and 3 percent of caustic soda (34 B.). After 20 minutes 1 percent of formic acid was added. After 20 more minutes 2 percent of formic acid was added. The heat was shut off and 5 percent of Levamine Red KB-S (S-chloro-o-toluidine, diazotized and stabilized with sarcosine) was added. After treatment for 20 minutes it was rinsed, scoured and finished as usual.

The dyeing was a considerably brighter, more level and stronger red than a similar dyeing made without treatment with ot-sulfostearic acid.

Example 20 Naphthol AS-FGGR was dissolved with a small amount of alcohol, caustic soda 34 B. and water, then diluted to a 2 percent solution. The leather employed was chrome tanned syntan grain glove leather.

(A) The leather was sprayed with the above solution and then top sprayed with a 4 percent solution of Fast Orange Salt GGD.

(B) The leather was first tumbled with 4 percent of a-sulfopalmitic acid as a percent solution and then treated as inA.

(C) The leather was first sprayed with a 2 percent solution of ot-sulfopalmitic acid, and then treated as in A.

In the case of A, the dyeing was a weak green uneven dyeing. B and C were full, bright green, relatively even dyeings, C being slightly superior to B in levelness of dyeing.

Example 22 Example 21 was repeated with the exception that Naphthol AS-OL was used as the coupler.

In the case of A, the dyeing was a weak orange dyeing, B and C were brighter, deeper and more even dyeings.

It will now be seen that there is herein provided a procedure for the azoic dyeing of leather and products produced thereby which satisfy all of the objects of this invention, and others, including many advantages of great practical utility and commercial importance.

Since there are many embodiments of the instant inventive concept, and since there are many modifications of the embodiments hereinbefore described, it is to be understood that all matter herein is to be interpreted merely as illustrative and not in a limiting sense. Accordy,

What is claimed is:

1. A process for the azoic dyeing of leather comprising treating leather with an azoic coupling component devoid of sulf'onic and carboxylic solubilizing groups in the presence of an u-sulfo substituted long chain fatty acid and in the further presence of a diazo material selected from the group consisting of a diazotized aromatic primary amine devoid of sulfonic and carboxylic solubilizing groups and the combination of a diazotizable aromatic primary amine devoid of sulfonic and carboxylic solubilizing groups and a diazotizing agent to produce the reaction product of said coupling component and said diazo material.

2. The process of claim 1 wherein said a-sulfo substituted long chain fatty acid is an a-sulfoalkylcarboxylic acid having from 12 to 1;; carbon atoms.

3. The process of claim 2 wherein said a-sulfoalkylcarboxylic acid is selected from the group consisting of a-sulfolauric acid, u-sulfopalmitic acid and a-sulfostearic acid.

4. The process of claim 1 wherein said a-sulfO substituted long chain fatty acid is present in an amount of from 0.2 to 5 percent based on the weight of the leather.

5. The process of claim 1 wherein the leather is impregnated with said ot-SlllfO substituted long chain fatty acid prior to treating the same with said coupling component.

6. The process of claim 1 wherein said diazo material is a diazotized aromatic primary amine.

7. The process of claim 6 wherein said diazo material is added to the leather subsequent to the treatment of the same with said coupling component.

8. The process of claim 1 wherein the leather is sprayed with said coupling component and then top sprayed with a diazotized aromatic primary amine.

9. The process of claim 1 wherein said coupling component contains an aromatically bound free amino group.

10. The process of claim 1 wherein said coupling component is an acylacetic acid arylide.

11. The process of claim 1 wherein said coupling component is a pyrazolone.

12. The process of claim 1 wherein said coupling component is an aromatic hydroxy compound capable of coupling.

13. The process of claim 1 wherein said coupling component is a B-hydroxy aromatic carboxylic acid arylide.

References Cited FOREIGN PATENTS 9/1937 Great Britain. 4/1954 Great Britain. 

